Things You'll Need:
- Digital multimeter
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Step 1
Connect the probesConnect the probes to the digital multimeter.
Connect the black probe to the com (common) port and the red probe to the port marked with the Ohm symbol which looks like an upside down horseshoe. For those of you who remember Greek, the Ohm symbol is the Greek letter Omega.
This digital multimeter has banana jacks for the port plugs. Other digital multimeters may have screw in terminals or BNC plugs. -
Step 2
Alligator clips to make work easierUse alligator clips to attach to the digital multimeter probes. The alligator clips will allow you to work more hands-free and provide a better connection to the component. Use a red and black alligator clip to match the probes.
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Step 3
Connect the clips to the resistorConnect the alligator clips to each terminal of the resistor.
Most common resistors are the 4 color band type. The first two colors indicate values, the 3rd band indicates a multiplier, and the 4th band indicates % tolerance of the resistor value.
The pictured resistor is red (2), violet (7), orange (x 1000), and gold (5%). This resistor should then theoretically have a value of 2700 Ohms with 5% tolerance of the value. The lower the tolerance value, the better the resistor. 5% tolerance is about as good as a standard resistor as you can buy at stores like Radio Shack. -
Step 4
Set the dial for Ohm testTurn the digital multimeter dial setting to Ohms (Omega).
Some less expensive digital multimeters have Ohm settings with multipliers (x 100, x 1000, etc). The digital multimeter shown is auto ranging so the multiplier will be shown in the screen with the reading. -
Step 5
27.02 k Ohms - the test is a successTake the digital multimeter reading. The pictured test shows a value of 27.02 k Ohms. The resistor value is therefore 2702 Ohms. This value is well within the 5% tolerance variance from 2700 Ohms. The resistor is ready for your project.
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Step 6
Touch probes on each terminal of the resistorTo test an in-circuit resistor with a digital multimeter, use steps 1 and 4 above. Make sure there is no voltage active in the circuit board. You will probably have to use the probe tips unless you have really small alligator clips. Touch each probe to a terminal of the resistor. For resistor testing you can touch either terminal with the black or red probes.
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Step 7
Sucess!Take the digital multimeter reading. This resistor has the color code green, brown, brown, gold, and should therefore have the value of 510 Ohms. The digital multimeter reads 509 Ohms. The digital multimeter test shows a good resistor.













Comments
sonni57 said
on 3/30/2009 I've never heard of a digital multimeter. Thanks for the info.
stlscientist said
on 3/27/2009 These are sooo handy to have around. When my laptop died I was able to figure out it was the cord and not the laptop. The store wanted to send it off! Saved me time and money.